grapnel vs mud hook

grapnel

verb
  • To connect (ships) with a grapnel. 

noun
  • A grappling iron. 

  • A device with a multiple hook at one end and attached to a rope, which is thrown or hooked over a firm mooring to secure an object attached to the other end of the rope. 

  • A small anchor, having more than two flukes, used for anchoring a small vessel. 

mud hook

How often have the words grapnel and mud hook occurred in a corpus of books? (source: Google Ngram Viewer )